#include <bits/stdc++.h>
using namespace std;
int main (){
	int x,y,n;
	cin>>x>>y>>n;
	float o,z;
	o=(x+y)*0.9;
	z=n-o;
	cout<<fixed<<setprecision(1)<<z;
}
/**************************************************************
	Problem: 1598
	User: shiruoxi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/